docs: def extract_exposure_metadata(dstore, what):
      """
      Extract the loss categories and the tags of the exposure.
      Use it as /extract/exposure_metadata
      """
      dic = {}
      dic1, dic2 = dstore['assetcol/tagcol'].__toh5__()
      dic.update(dic1)
      dic.update(dic2)
      if 'asset_risk' in dstore:
          dic['multi_risk'] = sorted(
              set(dstore['asset_risk'].dtype.names) -
              set(dstore['assetcol/array'].dtype.names))
      names = [name for name in dstore['assetcol/array'].dtype.names
               if name.startswith(('value-', 'number', 'occupants_'))
               and not name.endswith('_None')]
      return ArrayWrapper(numpy.array(names), dic)